docs: add EverMind sponsor section

[Yangtze-Seventh]

Summary

• add a compact EverMind sponsor section after the project introduction in the English and Chinese READMEs
• add the supplied 1920×576 Archify × Raven banner as an unchanged repository asset
• link the banner and Raven name directly to EverMind-AI/Raven
• briefly explain how Raven and Archify work together without changing the existing product copy
• expand the README scanability budgets only enough to cover the new sponsor block

CI maintenance

The current base branch already fails zip-freshness: the committed archify.zip is missing trailing blank lines present in two source reference files. A separate second commit rebuilds the archive with the repository's existing scripts/build-zip.sh; it does not change the Skill source or sponsor content.

Testing

• node --test archify/test/readme-showcase.test.mjs archify/test/cursor-onboarding.test.mjs — 6 tests passed
• git diff --check
• verified README.md and README_EN.md remain identical
• verified the committed banner is byte-for-byte identical to the supplied original image
• rebuilt archify.zip and recursively compared it with a second fresh build — no differences
• unzip -tq archify.zip — no compressed-data errors